Rheostat



A. w. BRICE.

RHEosTA.

APPLICATION FILED MAY I6. 1916.

Patented Feb. 14, 1922.

2 SHEETS-SHEET 2.

Am .I -n. @ma m LLLULIH ,es ao e 16 1%' z WVM/70H' UNIT ED 3ST AT ES PATENT OFFICE.

ARTIIUR :WELLINGTON lERICE, OF ROCHESTER, NEW YORK, ,ASSIGNORa BY 'MESNE ASSIGNMENTS, TO UNITED SHOE MACHINERY CORPORATION, OF PATERSON, NEW JERSEY, A CORPORATION OF NEW JERSEY.

RHEOSTAT.

Application filed May 16, 1916.

'To @ZZ @710m it may concern:

itlrnoivn that l, ARTHUR lV. BRICE, a cnizen of the United States, residing at chester, .in the county of Monroe and l `l" i l v I .i ne ,t Bev; fork, ha\e invented certain Improvements in 'Rheostats, ot which the following description, in connection with the ,accompanying drawings, .is Ya specifican.`lil e reference characters on the draw- I indicating lilre parts in the several figuL Vs.

'This invention relates to rheostats and is designed to provide an improved rhcostat of compact construction affording' a wide range of adjustment for. variable re sistance.

VRheostats, as heretofore proposed, have been subject to thedisadvantage of affording only a limited number of' contact points tor introducingfixed amounts of resistance `without any means whereby amounts ot risif'ance intermediate these fixed points can be secured. il further disadvantage tound in rheostats.r particularly those designed ttor general use, has been the lael;

means arranged, under certain condito reduce the adjusted resistance in adently ot the means by which the reince has been initially adjusted. lt is im jnently desirable, when rheostats are inv nose-1l in the circuit-s ot translating1` dey to provide a normal maximum rerance vvhen the device is inoperative, and

sistance when theA device is in use. ltalso been round that, when rlieostats as ieretoifore proposed are used in translating c'renits ot relatively high voltage very mai `y to reduce the voltage, the resistance ement nas become unduly heated, a condition which is dangerous, in that it is possible Specification of Letters Patent.

nomentarily or temporarily to decrease the Patented Feb. 14, 1922.

Serial No. 97,913.

and arrangementof resistance element and 'co-operating resistance-varying means Ywhich, as herein shovvn, embocies a coil or spiral vot resistance material having an edge exposed for contact with a movable contact member constructed Ytor adjustment to engage the exposed edge of the coil from a point adjacent to one end of the coil transversely ot the coil for a distance less than its width, and with a second movable contact member.constructed and arranged for adjustment to engage the exposed edO'e of the coil from a point adjacent to the other end ot the coil transversely of the coil for a distance'less than the Width of the coil. Such a construction permits various arrangements ot circuit connections, one ot which, as shoivmenables `the second contact member to be placed iny a normally open shunt circuit, which, when closed, will cause the second member to act as auxiliary resistance controlling means temporarily to out outV an additional and determined amount ,ot resistance. Preferably, the aggregate transverse adjustment ot the two contact members approximates the transverse ividth ot the coil and may beeither equal to said transverse Width or less than such Width. As the two movable Contact members operate trom opposite sides of the coil, -it will bev obvious that any desired 'rotated progressively to engage the exposed tace ot' the resistance element from a point adjacent to one end of said element tovvard the other end. This arrangement of partsV not only insures adequate contact but enables the interposed resistance accurately tol be determined and easily to be controlled.

il furthery feature oi' the invention consists in a resistance element comprising an cessive convolutions which are of very niaterial assistance in radiating heat from the resistance material. Vith a flat coil of' this type supported in a horizontal position, the corrugations will form vertically extending passages through which the einanated heat naturally ascends and through i which the surrounding and cooler air readily circulates. This coolingair circulation is facilitated by the employment of an enclosing casing for the resistance element with ventilation openings therein.

A further feature of the invention consists in combination with a coil of resistance material having an exposed contact edge, of Complemental' Y electrically `interconnected movable contact members constructed for adjustment progressively to engage correspondingpoints in the exposed edges of the l coil from adjacent to one end ot' the coil transversely of the coil in opposite directions.` Suchl adjusting movement may take place from the inner side of the coil' outwardly or vice versa, and the provision of compleniental contact members substantially increases the surtaceot electrical contact.

These and other features and advantages` will be more'clearlyy apparent from the detailed description following, read in connection with the accompanying drawings, illustratinv` a preferable.embodiment of the inventicn, and in which, v Y V Figure 1 is a plan view of a rheostat constructed in accordance-with the present invention, the'4 cover of the casing-being re-l moved Fig.

2 'is a transverse vertical section through the rheostat with the cover applied to the casing; y

Fig. 3 is a diagrammatic view illustrating the rheostatin connection with a translating circuit; and Y Fig. V4 is a fragmentary perspective view oip' the rheostat casing cover showing the adjvustment handles with "their indicators and dials.

A suitable casing is provided for the resistance elenientand its controlling mechanisin, such as a base 2 provided with laterally offset-,feet 4l by means ,of which it Vmay be secured to a suitable support.' The base is preferably provided with an annular groove to receive the bottom edge of an annular side 6. A cover plate 8 preferably having its edges downwardly iianged to overlap the sides, is detachably secured to the frame by suitable means, such as the sleeved bolts 10 extending from the-base thro-ugh the cover plate and clamped thereto by suitable nuts.

The resistance element is supported horizontally intermediate the top and bottom of the casing between a series of spaced pairs or' upper and lower grid bars 12, the lower grid bars being supported from the base by suitable posts 14.'

The resistance element is in the form of a spiral coil of ribbon 16 of resistance material ...having its face corrugated transversely andy having a strip 18 of insulating material, such as mica, wound between the convolutions of the coil to insulate the separate convolutions from each other. The Hat spiral so formed presents a coil of resistance ribbon with exposed edges forming a flat contact surface. These coils are'insulated from the grid bars, between which they are supported,by means of plates 20 of insulation inserted between the grid bars and the edges of the coil at the top and bottom. The corrugations ofthe resistance ribbon 16 form in conjunctionwith the adjacent convolutions of the strip or' insulation, Ventilating. passages which, in the preferable use of the' rheostat, extend vertically so that the heat generated will ascend through these passages and enable the resist-ance element quickly to radiate any heat generated. Preferably, also, the sides and cover `Vplate or" the rheostat casing are provided with apertures to enable the outsideand cooler air to circulate through the vertical air passages formed by the corrugations ol the resistance ribbon. ln the drawc ings, the corrugations, of the ribbon are shown disproportionately large for clarity of illustration and preferably will be substantially reduced to provide an enlarged and more compact VVstructure offering a greater ai' tact. y

it one side ofthe casing, service connectors 22 and 2e are provided and are arranged to receive conductors Vfrom opposite sides of a service circuit, the current entering, for example, byrconncctor 24. At the opposite side of the casing a series of translating circuitconnectors 26, 28,30 and 32 are provided. VThe outer end oi .the spiral of resistance ribbon 16 may be connected as at 34 to a conductor 36 leading to the connector 28; The service current at one side, asthe return side, may be connected directly to translating circuit connector 26 by the conductor 38 extending across the rheostat from the servfor resistance regulating con- :ice connector 22. The inner end of the spiral or" resistance ribbon may be connected toy one side oi the circuit and a movable contact device is 1arovided which is arranged for Y 'outer ends of the spiral. shaft 'are supported in journal blocks 42 c two spaced contact members electrically interconnected and arranged to engage diametrically opposite corresponding points adjacent to the inner end of the spi-ral coil 16 and progressively and simultaneously to move uniformly outward transversely and radially of the coil toward the outer edge thereof, progressively cutting out successive convolutions of the spiral coil of resistance. Accordingly, a shaft 46 extends radially of the coil and terminates at points within the The ends of this having upstanding threaded studs 44 over which connector clips 50 are seated to bear against the blocks 42. A washer 46 of insulating material is seated over the studs and rests upon the upper face of the connector clips 50. A Sleeve 48 of insulating material having' a flange at its upper endv is seated on the studs above the washer 46 and insulates the studs vfrom the apertured ends of leaf spring arms l'seatin'g over the studs 44 and around the insulating sleeves 48 and appropriately clamped to the bearing block. In the drawings Ishow` a washer and nut seated over the upper end of the stud and Y clamping the clip and spring arm in place.

The spring arms 51 are secured to rigid bars 52, supported by and laterally offset from the grid bars 12 at opposite sides of the rheostat. The spring arms 51k tend normally to press the journal blocks and shaft downwardly toward the resistance member. It should be stated that preferably there are S pairs of upper and lower grid bars supporting the resistanceelement, arranged in two series of spaced bars, each series extending transversely of the spiral in the same direction, one series extending substantially at right angles to the other series. rlhe shaft `40 extendsbetween one of these series of spaced bars 12 and is pressed' downwardly in the direction of the exposed edge of the resistance member 16 by the supporting spring 'arms 51. Mounted on the shaft 46 and extending from points adjacent to the inner end of the resistance member radially eutof course, fixed on the shaft 40, with their contact ribs positioned to engage the inner end of the spiral 16 upon initial rotation .of the shaft. The shaft is rotated to secure 'determinate adjustment of the contact ribs by means' of a crown rack 58, which may be segmental or circular, carriedby a sleeve clamped on the shaft 46 and insulated therefrom. The shaft 40 is turned to rotate the sleeves 54 and move the contact points of the helical ribs radially outward 'through a pinion 62 carried on a spindle 64 extending through the cover F3 ff the rheostat casing and attached to an operating knob 66. v'lie portions of the completically ,above the radial line oi contact with the resistance member are always pressed into contact with the exposed edge of the resistance member by the action of the spring arms 51,' the use of two contacting ribs insuring ample surface contact.

The inner end 68 of the coil 16 of resistance ribbon is connected to a conductor Y() extending from the service connector 24. The

connector plates 48 at the supported ends ot the shat 46 are electrically bridged by conductors T2 having their ends connected to each other` and to the conductor "(6, as at T4. Tie conductor i6 extends from this point across the rheostat to the translating circuit connector 32. Y

From the described construction it will be evident that the service current will flow from the service connection 24 threugh conductor to the inner end 68 of the resistance element 16 assuming that the contact members have not been rotated to engage the exposed edge of the r tance element) and will flow through the successive con volutions of the helical coil 16 to its outer end 34' and thence to suitable translating C ices and baci to the opposite side of the service circuit. Assuming, however, that the operating handle 66 has been turned to rotate the shaft 46 and position the helical ribs 56 for contact with the exposed edge of the rcsistanc-e coil at a point between its inner and outer ends, the service current will enter at connector 24 and flow to the contact point of the helical ribs 56 with the helical coil 16, thence around the coil outwardly to its outer terminal and to the translatin device or devices and will return to th po. te side of the seri' -e circuit.

In order accurately to determine the proiortion oi resistance cut ont by the contact point of the helical ribs 56, a pointer T6 is fixed to the spindle 64 of the crown at a pointadjacent the handle 66, this pointer cooperatingl with a circular dial 'T8 which will have imprinted thereon, or otherwise indicated, a scale of the proportion or amount of resistance cut out by the Contact points of the helical ribs 56 at the point of adjustment of the shaft 46 indicated by the pointer 76 and dial 78. rlhe pinion 62 may be retained in mesh with the crown rack 5S, when a segmental rack is employed, by pins 8O co-operating with the pointer 7 6 to prevent the operating knob from being turned suiiiciently far to move the pinion out of engagement with the rack teeth of the segment. Y

Y i short counter shaft 82 is mounted between spaced pairs Voi: grid bars 12 in the `plane of the shaft 40 and at right angles tending inwardly thereon for a distance toV approximate the outermost contact point or' the helical ibs 56, is a sleeve 88 fixed to the shaft and havin@ thereon a helical contact rib 90 Vwhich extends the length of the sleeve. Adjacent to the end of the sleeve 88 the shaft 82 is supported in a second bearing bloclr 92 constructed ,similarly to the bearing blocks 42 heretofore described and vsimilarly supported by a spring arm 94. The shaft 82 is designedA to be rotated to bringits' helical contact rib 90 against the exposed edge of the helical resistance coil 16 adjacent to its outer end and progressively to move its contact point radially inward as the shaft is rotated. Accordingly, a sleeve 96 is clamped on the shaft 82 and insulated therefrom and carries a segmental crown rack 98 arranged to beengaged by a pinion 100 carried by a spindle 102 (F ig. 1) extending downwardly' from the cover 8 of the casing and supported therefrom, itsV upper end boing provided with an operating knob 104 and with a pointer 106 o o-operating with an annular dial 108 and with stop pins 110 in a similar manner to the spindle 64, knob 66, pointer 76, dial 78 and pins 8() oi" the maincontact adjusting mechanism. In the disclosed construction it is intended that in the position of limit ot movement the shafts 40 and 82 will position their contact ribs out oi' engage- 'ment with the helix so that thel entire resist- Vauxiliary resistance cut-out.

ance 'of the helixV may beinterposed. rlhis arrangement, however, may be varied with' different circuit connections.

The shaft 82 with its associated parts and operating mechanism may be 'electrically connected in such manner as tol constitute an A conductor 112 ma f be connected to the journal block 84 in a manner similar to theA conductor l2 attached to the blocks 42, to extend from the journal block to the translating circuit connector 30 of the rheostat and may be connected in shunt with a portion of the resistance circuit leading to suitable translating' devices.

ln order clearly to understand Vthe relation of the resistance adjustments afforded by the described mechanism, reference may be had to the diagrammatic view shown in l? ig. 3 of the drawings, in which similar numerals designate similarstructural parts and connections as heretofore described.

issuming that the knob 66 has been ronection 2 to the shaft 40 and to the Vcontactpoint oi .the helical ribs 56 with the resistance coil; around the resistance'coil 16 outwardly to the outer terminal 34 of the coil, thence lby conductor 36 to outlet terminal 28 et'V the rheostat casing and by a conductor 116 to one side of suitable translating devices indicated generically at V118. From the opposite side of the translating devices,

thecurrent will flow by conductor 120 to connector 26 of the rheostat andthence byY return conductor 38 to the service connector i 22 of the rheostat and back to the opposite side oit the current source 114.

rlhe resistance cut-out comprising the shalt 82 with its sleeve and helicalY contact rib, is connected by the conductor 112 to the connector 30 and extends from .this connector by a conductor 122 to a Vjunctionv with the conductor 116 of Ythe main circuit, a suitable switch or circuit closer 124 being ,interposed between the connector 8O and the line or conductor 116. This switch may 'remain open until suoli time as it is desired to close the shunt-circuit temporarily to cut out that portion of the resistance determined by the adjustment and contact point of the helical rib 90.

issuming that the shaft 40 has beenV adjusted, as heretofore described, and that the shaft 82 has been similarly adjusted to advance the contact point ci the helical rib 90 inwardly/ Voit the oiiterend oi the resistance coil 16, the path traversed by the current with the shunt circuit closed through the circuit closer 124, willbe as follows: from the current source 114 through service connector 24 and conductor 70 to shaft 40 and the contact point of the helical ribs 56 with the resistance coil; thence through the coil romthis point around and outwardly of the coil to the adjusted contact point of the helical rib 90 of the auxiliary resistance cut-out; thence through sleeve 88 and its shaft and by conductor 112 to connector 30 and by wire 122, including circuit closer 124 to the conductor 116, through the translating devices 118 and byV return-conductor V120, connector 26 and 'conductor 38 back tothe service connector 22 and to the opposite side of the current source 114. In this last circuit, that portion vof the coil of resistance material inwardly of the contact points of the helical ribs 56 and outwardly of the contact point ot the helical rib 90, is 'cut out ot resistance during the time the shunt circuit is closed through 124.

It may be desirable in some cases to include in the translating circuit jvith the Atranslating' devices il, a motor, such as a motor tor turnishing the operating poiver for a machine employing marking device electrically heated and forming the translating device. In such an event, the conductor at the intake side otthe circuit may have a branch'l28 extending` to connector 32 of the rheostat and, by a conductor 130 having a switch 132 interposed therein, to one side ot a motor 126, the c'urrent flowing through the motor and from the Opposite side of the motor by a conductor 13ste effect a junction with the return conductor 120 of thepmain circuit. These parts of the motor circuit in the diagrammatic view in F ig. 3 are indicated in light lines, While the main circuit is indicated in heavier lines. The motor circuit may be entirely omitted Without interferring with the operation of the main circuit or with the rheostat. ln such an arrangement one ot the circuit connectors (32) may be dispensed with.

From the foregoing descriptionit will be evident that my invention provides a rheostat oi compact construction offering a ivide range of adjustment with accurate control and providing in addition, a particularly advantageous construction oi' resistance element.

The described and illustrated arrangement of circuit connections for the rheostat, While preferable and particularly advantageous, is purely arbitrary, and the circuit connections may be. varied for different conditions.

Having thus described my invention, what l claim yas neiv and desire to secure by Letters Patent ofthek United States is l. A rheostat comprising a spiral of sist'ance material having an edge exposed for contact, a movable contact member constructedV for adjustment to engage the exposed spiral edge transversely from a point adjacent to one end of the spiral across the spiral., and a second movable contact member constructed for adjustment to engage the exposed spiral edge transversely rom a point adjacent tothe other Vend of the spiral.

2. A rheostat comprising a spiral of resistance material having one edge exposed for contact, a movable contact member constructed 'for adjustment to engage the exposed' spiral edge radially liroma'point adjacent toone end of the spiral across the spi "al, anda second movable contact member constructed tor adjustment to engage the exposed spiral edge radially from a point adj acent to the other end ot the spiral.

3.' A' rheovs'tat comprising a spiral of resist-ance material having an edge exposed for Contact, a movable contact member constructed for adjustment to engage the exposed spiral edge transversely from a point adjacent the inner end ot the spiral toward the cuter end of the spiral, and a second movable contact member constructed for adjustment to engage the exposed spiral edge transversely from a point adjacent to the outer end ot the spiral tor a distance less than the Width of the spiral.

l. A rheostat comprising a flat coil of resistance material having one edge exposed Jfor contact, a movable contact member constructed for adjustment to engage the exposed edge et' the coilV transversely from a point adjacent to one end of the coil toward the other end, and a second movable contact member constructed :tor adjustment. to engage the exposed edge ot the coil transversely from a point adjacent to the other end of the coil toivard said rst named end.

5. A rheostat comprising a' flat coil of resistance material having one edge exposed for contact, a movable contact member constructed for adjustment to engage the exposed edge off the coil from a point adjacent to the inner end ot the coil transversely outwardly, and a second movable contact member constructed for adjustment to engage the exposed edge of the coil from a point adjacent to the outer end of the coil transversely inwardly of the coil, one of said contact members being arranged for connection to a translating circuit.

G. A rheostat comprising a flat spiral ot resistance materia-l having one edge exposed for contact, a rotatable contact member constructed for rotary adjustment progressiveljf.' to engage the exposed spiral edge from a point adjacent to one end et the spiral transversely ot the spiral, and a second rotatable contact member constructed ter rotary adjustment progressively to engage the exposed spiral edge 'trom a point adjaca-mt to lthe oppositeend ot tric spiral t ansversely ot the helix toward said ifirst named end` one o'll said Contact members being arranged for connection to a translating device.

A rheostat comprising a liat spiral oiE resistance material havingr one edge exposed for contact, a rotatable member having a helical contact rib constructed lor rotary adjustment progressively to engage the exposed spiral edge if'rom a point adjacent to one end ot the spiral transversely of the spiral, and a second rotatable member having a helical contact rib constructed for rotary adjustment progressively to engage the -exposed spiral edge from a point adjacent to the opposite end of the spiral transversely of the spiral toward said first named end, one of said contact members being arranged for connection to a translating device.

8. A rheestat comprising a flat spiral of resistance material having one edge exposed 'for contact, a movable contact member arranged for connection to a resistance circuit and constructed for adjustment to engage the exposed spiral edge from a'point adjacent to one endof the spiral transversely oi the spiral `and a second moif'able contact member constructed for adjustment to engage the exposed spiral edge from a point adjacent to the other end or" the spiral transversely of the spiral and arranged for connection in shunt With the resistance circuit.

9. A rheostat comprising afflat spiral of resistance material having one edo'e exposed for contact, a rotatable Contact member constructed for rotary adjustment progressively to engage the exposed spiral edge from a point adjacent to one end or the spiral trans versely of the spiral and arranged i'or connection to a resistance circuit, and a second Ifor contact and having its ends arranged tor l Y movable contact member arranged for con-- exposed spiral edge from a point adjacent rotatable member constructed 'for rotary adjustment progressivelyV to enoage the exposed spiral edgev from a point adjacent to the first named spiral end transversely ot the spiral to and arranged for connection in shunt With the resistance circuit,

10. rheostat comprising a flat spiral ot resistance material having one edge exposed for contact, a rotatable member having a helical contact rib thereon constructed for rotary adjustment progressively to engage the exposed spiral edge along a line-troni a point .adjacent to one end of the spiral transversely of the spiral and arranged for connection to a resistance circuit, and a second rotatable member lia-ving a helical contact rib constructed for rotary adjustment progressively to engage the exposed'spiral edge along a line from a point adjacent to the opposite end of the spiral transversely of the spiral and arranged for connection in shunt with the resistance circuit. a

11. A rheostat comprising a flat spii' resistance material having one ed exposed forcontact and having its ends arranged Vfor connection to one side vet a niain circuit, a movable contactineniber arranged for connection to oneiside of the maiiicircuit and lconstructed for adjustment to engage the; exposed spiral edge from a pointV adjacent i Atoone end ot the spiral transversely of the spiral, anda second movable member ai'- ranged for connection in-l shunt to the main circuit and constructed for adjustment to engagetheexposed spiral edge from a pointadjacent tothe opposite end of the spiral transversely of the spiral for a distance less than the Width of the helix.` f

1.2. A rheostat comprising a fiat spiral of resistance material having one edge exposed connection toene side of a main circuit7 a nection to said side of the main circuit and constructed forA adjustmentv to engage the to one end of the spiral transversely of the spiral, and asecond movablemember arranged for connection in shunt with the same side of the main circuit. and constructresistance material having one edge exposedV Jfor contact and having its ends arranged for connection to one siderof a main circuit, a

rotatable contact member constructed forY` rotary adjustment progressively to engage the exposed spiral edge from a point adjacent to one end ofthe spiral transverselyvof the spiral and arranged for connection to said side of the main circuit, and a second rotatable contact Vmember constructedV for rotary adjustment progressively to engage tlieexposed spiraledge from a point adjanection in shunt tothe same side ofthe main circuit.

sa cent to the opposite end or" the spiral trans-` 1 ,versely of the spiral and arranged for' consource oit current and aV translating device having one edge exposed Vfor contact` and havingits ends arranged `for connection to one side ofV aY main circuit, a rotatable contact member constructed for rotary adjustment progressively toenga-ge the exposed spiral edge from a point adjacent to one end of the spiral transversely Vofthe spiraljand arranged for connection to said sideieoi' the main circuit, and a second rotatable contact member constructed for rotary adjustment progressively to engage the exposed spiral edge from point adjacent to the opposite end oi the-spiral transversely ci the spiral;V

said second contact member being arranged iior connection in shunt with the saineside of the main circuit to which the iirst men-g,

tioned contact memberniay beconnectejd.`

15.1 A'rheostat comprising a casingLa lat v,spiral of resistance material mounted with;

in the casing and insulated therefrom and having insulation `between successi-ve convolutions thereof, a rotatable shaft carrying a contact member constructed for rotary ad-,

justment progressively to Vengage the exposed spiral edgealong a line transversely. of the los` iio

spiral from a point adjacent to one end of the spiraha second rotatable shaft carrying a contact member constructed for rotary adjustinent progressively to engage the VVexposed spiraledge along a line transversely of the spiral from a point adjacent to the,V

opposite endet Vthe spiral fand arranged for connection to the translating circuit, and

means lor rotating said shafts l determinately to" position their contacts relatively tothe exposedV edge ofthe spiral resistance; Y 16. A rheostat lcomprising a casing, aV llat spiral of resistance Vmaterial mounted Withiso ' uniform movement ot s in the casing and` insulated therefrom and having insulating material interposed between its successiverconvolutions, a rotary shaft, a helical contact rib projecting from the shaft and constructed tor rotary adjustment progressively to engage the exposed spiral edge `along a line transversely or" the spiral from a point adjacent to the inner end of the spiral, a second rotat ble shaft having a helical rib projecting therefrom constructed torrotary adjustment progressively to engage the exposed spiral edge along a line transversely ot the spiral troni a point adjacent to the outer end ot the spiral, means to support said shafts to maintain their helical ribs in contact with the eX- posed spiral edge, and means independently to rotate said shafts determinately to adjust the contact points ot their helical ribs relatively to the convolutions of the spira-l resistance.

17. A rheostat comprising a 'tlat spiral 01"' resistance `material having an edge exposed tor contact, and complemental electrically interconnected movable contact members constructed and arranged progressively to engage opposite points on corresponding convolutions of the spiral from a convolution adjacent to one end transversely of the spiral toward the other end said contact members being constructed Jr'or simultaneous and uniform movement in opposite directions toward the terminal convolution at said other end.

18. ill. rheostat comprising a tlat spiral ot resistance material having posed for Contact, and complemental elec.-

rically. vintercormected rotatable Contact members constructed tor rotary adjustment progressively to engage the exposed edge et the spiral at oppositepoints on corresponding convolutions ot' the spiralifrom the convolution at one end oil' vthe spiral t f versely ot the spiral toward the other end. with means 'for eniectinc simultaneous and cont ct members in opposite directions along lines t i versely ot the spiral and toward the tern.. convolution at said other end ot the spiral.

resistance material. having one edge exposed tor cont-act, and complemental electrically interconnected rotestable'- shatts havin@- helical contact ribs proj cting there'l and constructed prog Y one edge en 19. Si .rheostat comprising a flat spiral oi?y translating device a rotatable member airanged for connection to said ycircuit and having a helical contact rib projecting` therefrom, arranged, when rotated. progressively to engage the exposed edge ot the coil troni a point adjacent to one end ot the coil toward the other end.

2i. i\ rheostat comprising a iiat coil ot resistance ribbon havii one edge exposed torcontact a d Aormin a tint contact surface and having its tace transver. ly corrugated to torni air passages with insula tion between the 'faces ot successive convolutions ot the coil.

y 22. A rheostat comprising a coil ot sistance ribbon having` one edge exposed tor contact and having its tace ransvcrsely corrugated to if'orm air p ges, with insulation betweenthe faces ot succcssiveconvolutions ot the coil.

23. A rheostat comprising a tlat coil oit resistance ribbon having one edge exposed tor contact and forming a fiat contact surif'ace and'havingits tace transversely corrugated to 'torni air passages, with a ribbon ot insulation wound between the successive convolutions ot the coil.

24. A rlieostat comprising a casing having ventilation openings in its sides and top, a resistance element supported within said casing between its top and bottom and insulated therefrom and comprising a` iiat horizontally positioned coil ot resistance ribbon having its t'ace transversely corrugated to provide a series oit' vertical air passages.

25. rheostat'comprising an elongated resistance ribbon arranged in insulated convoirtions having` exposed edges and constructed to torm ventilating air passages eX- tending` transversely of the ribbon tace and lengthwise ot the ribbon.

2Q. A.' rheostat comprisingran elongated resistance ribbon-ar anged in insulated convolutions providing a series of Ventilating air passages between the ribbonand its insulation. f

27. A rheostat construction comprising a casing having ventilating openings in its side, and an elongated resistance element spaced and insulated tromthe bottomand sides ot the casing and arranged in insulated convolutions providinga series ot ventilating air passages substantially perpendicular to the bottom ot the casing.

28. *er rheostat construction comprising a casing' having ventilating` openings and a resist-anne element supported within and spaced and insulated from the walls of the casing` and .formed in insulated convolutions providing a series ot' ventilating air passages extending lengthwise ot1 said element.

29. An elongated resistance element arranged to be interposed between a current source and a translating device and having one face exposed for Contact, a contact mem- Y ber mounted for adjustment progressively to contact with said face of the resistance from a point adjacent to one end of the resistance toward and from the other end, and a second Contact member mounted for adjustment progressively to contact with said face of the resistance from a point adjacent to the other end of said resistance toward and from the first mentioned end, and manually operablev means for effecting determinate adjusting movements of said contact members.

30. Ank elongated resistance element arranged to be interposed between a current source and a translatingdevice and having one face exposed for contacta contact member mounted for adjustment progressively to contact with said face of the resistance from a point adjacent toone end of the resistance toward and from the other end, and a second and independent Contact member mounted for adjustment progressively to contact withV said face of the resistance from a point ad-V jacent 'to the other end of said resistance toward and from the first mentioned end,-

" and manually operable means for effecting aov V sively toY contact ,with said Vface of the resist- Y mentioned end,

theV other end j of Y towardfthe first mentioned end, and man- .'60

Y movements ofsaid 45 ance from a point adjacent to the other end of said vresistance'toward and from the first and manually operablemeans for effecting determinate adjusting contact members.

32. An elongated resistancev element arranged to be Vinterposed between a current source and a transmitting device andformed in insulated convolutions having one face Vexposed for contact,a contact member arranged to engagegsaid resistance face Yand f mounted foradjusting movement to cut out of .circuit portions of said resistance element from one end` of the resistance Y element toward the other end, a second contact Vmember arranged to engageV said resistance face and' mounted lfor adjusting movement to cut outof circuit portions of said resistance from `said resistance element ually operable means for effecting independent and determinate adjusting movements of said contact members. Y i u 33. A rheostat construction comprising an s elongated resistance Velement disposed in insulated convolutions having exposed contact faces lying in the` samel planej .a movable contact member arranged for vconnection in circuit between a current source and a trans-V lating device and constructed for adjustment to engage said contact faces from a point adjacent to one end of said element, toward the other end, and a second contact member arrangedfor connection in shunt' withl said circuit and constructed for. adjustment to 'engage said contact taces from a `point adjacent to said other` end of the` resistance Yelement toward the first named end. Y

elongated resistance element disposed in in- 34. A rheostat construction comprising` an sulated convolutions having exposed contact` faceslying in the same plane, a movable contact member arranged for connection in circuit between a current source'and a translating device and constructed for adjustment to engage said contact faces from a point adjacent to one end of saidelement toward the other end, a second 'contactmember ar-V ranged for connection Yin shunt with said circuit and constructed for adjustment to en-V gage said contact faces from a point adjacent to said other end of the resistance element' toward the first named end, and man ually operable means for effecting adjusting movements ofsaid contact members.

35. Arheostat construction comprising a coiled resistance element having Yinsulated convolutions presenting exposed contact faces located in the same plane, a movable contact member arranged for connectionin circuit with a current source and a translating device and constructed for adjustmentv to engage said contact faces from a point adjacent'to oneend of said element towardv the other end, and a` second movable con-1 tact member arranged for connection in shuntwitli said` circuit and constructed for adjustment to engage said contact faces from` a point adjacent to said other end of the resistance element toward said first named end. Y j Y .36; A rheostatconstruction comprising a coiled resistance element having insulated convolutions presenting exposed contact aces located in the same plane, a movable contact'member arranged for connection in circuit with a current source and a translating device andV constructed for adjustmentV to engage said contact faces from a point j adjacent to one end of said element toward the other end7 a secondA movable contact member arranged for connection in shunt justment to engage said contact faces from a point adjacent to said other end` of the resistance element toward said firstf named end, and manually operable means for independently effecting determinate adjusting movements of said contact members. l

37. A rheostat construction comprising a with said circuit and constructed for ad#Y Y flat spiral of resistance ribbon having insulated convolutions presenting exposed contact edges located in the same plane, a movable Contact member arranged for connection in circuit between a current source and a translating device and constructed for adjustment to engage said contact edges from a point adjacent to one end ot' the ribbon toward the other end7 and a second movable contact member arranged for connection in shunt withV said circuit and constructed for adjustment to engage said contact edges from a point ad'acent to said other end oit the ribbon toward the iirst named end.

'38. A rheostat comprising a flat coil of resistance material having one edge exposed for contact, and a rotable resistance-varying contact member arranged to be moved progressively to engage said exposed edge with a wiping contact.

39. A rheostat comprising an elongated resistance element having a plane 'face exposed for contact, and a rotable resistancevarying member having a spiral contact surface arranged progressively to engage said exposed contact face.

40. Arheostat comprising a spiral resistance element having a plane face exposed for contact, and a rotatable resistance-varying member extending transversely of the coils of said element and having a spiral Contact rib arranged to be moved by rotation of said member progressively to engagel the exposed plane face of the convolutions of said spiral resist-ance element with a wiping member having a spiral contact surface arranged progressively to engage said exposed contact tace.

A rheostat comprisinga ribbon of resistance material having one edge exposed and forming a plane contact surface, and

having its 'tace transversely corrugated to 'torni air passages.

43. A rheostat comprising a coiled ribbon of resistance material having one edge exposed and forming a plane contact surface,

and having its face transversely corrugated to Jform air passages with insulation between the :taces ot successive convolutions of the coil.

In testimony whereof I have signed my name to this specification.

ARTHUR WELLINGTON BRICE.

Certificate of Correction.

t is hereby certified that in Letters Patent N o. 1,406,257, granted February 14, 1922, upon the application ott Arthur Wellington Brice, of Rochester, New York, for an improvement in Rheostats, errors appear in the printed specification re-l quiring correction as follows: Page 3, line 109, for the Word helical read resistcmoe; page 5, lines 52 and 62, claims 1 and 2, after the Wort spiral insert the Words across the spiral; same page, lines 73 and 711, claim 3, strike out the Words for a distance less than the Width and insert instead toward the amer end,- page 6, line 23, claim 9, strike out the word to and lines 55 and 56, claim 11, strike out the Words for a distance less than the Width of the helix same page, lines 124 and 125, claim 15, strike out the Words and arranged for connection to the translating circuit, page 8, line 47, claim 32, for the Word transmitting read mnsloting; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Oiice.

Signed and sealed this 19th day or' September, A. D., 1922.

[SEAL] WM. A. KINNAN,

Actif/Lg Commissioner of Patents.

Certificate of Correction.

t is hereby certied that in Letters Patent No. 1,406,257, granted February le, 1922, upon the application of Arthur lVellington Brice, of Rochester, New York, for an improvement in Rheostats, errors appear in the printed specification re-a quiring Correction as follows: Page 3, line 109, for the Word helical read resistance; page 5, lines 52 and 62, claims 1 and 2, after the Word spiral insert the Words across the spiral; same page, lines 73 and 711, claim 3, strike out the Words for a distance less than the Width and insert instead toward the inner emi,- page 6, line 23, claim 9, strike out the Word to and lines 55 and 56, claim 11, strike out the Words for a distance less than the Width of the lieliX same page, lines 124 and 125, claim 15, strike out the words and arranged for connection to the translating circuit page 8, line 47, claim 32, for the Word transmitting read trams- Zaii/rig; and that the said Letters Patent should be read with these Corrections therein that the saine may coliform to the record of the case in the Patent O'fice.

Signed and sealed this 19th day or' September, A. D., 1922.

[SEAL] 1WM. A. KNNAN,

Acting Commissioner of Patents. 

